1. Technical Field
The present disclosure relates to a transmission gear control apparatus that controls an automatic transmission on the basis of a vehicle state and, in particular, to gear change control in the case where a torque converter that has a lock-up clutch is provided.
2. Description of Related Art
Conventionally, in a stepped automatic transmission that is mounted on a vehicle, a favorable shift schedule that corresponds to a vehicle state including a vehicle speed, an accelerator operation amount, and the like, for example, is set in an aspect of a gear change chart, and an appropriate transmission gear stage for a current driving state is selected by referring to this gear change chart, that is, a gear change map. A favorable engagement state of a lock-up clutch in a torque converter is also set in such a way as to correspond to the vehicle state, and the lock-up clutch is thereby controlled in an appropriate engagement state for the current vehicle state.
For example, for a control apparatus described in Japanese Patent Application Publication No. 2012-107537 (JP 2012-107537 A), a lock-up region, a flex lock-up region, and a torque converter region are set in an aspect of a lock-up chart in advance for each of the transmission gear stages of the automatic transmission. In the lock-up region, the lock-up clutch is completely engaged. In the flex lock-up region, the lock-up clutch is controlled in a slipped state. In the torque converter region, the lock-up clutch is disengaged. Then, the lock-up clutch is controlled in the appropriate engagement state for the current vehicle state by referring to the lock-up chart, that is, a lock-up control map.
More specifically, the torque converter region and the flex lock-up region are shown in a lock-up control map that is exemplified in FIG. 5 of the same literature. In the torque converter region, an accelerator operation amount at a fourth gear stage is equal to or larger than a specified value. In the flex lock-up region, the accelerator operation amount is smaller than the specified value. That is, in the region where the accelerator operation amount is equal to or larger than the specified value, the lock-up clutch is disengaged, so as to suppress generation of booming noise and the like in a vehicle cabin. In addition, a flex lock-up on line, a flex lock-up off line, and the like are set between the two regions.